Divers and low lying vessels such as certain motorized craft, sailboats, kayaks, or underwater vehicles on the surface are nearly invisible on the water due to their size and they have little or no expression on other vessels' radio detection and ranging (RADAR) screens. There is a clear danger of being run down by ships or being lost at sea in the event of trouble.
Passive signal devices such as RADAR reflectors are known that are currently mounted high on the masts of motorized crafts, sailboats and working boats to increase their potential appearance on the radar screen of other vessels. These devices become critical equipment at night or in fog and to avoid collision and facilitate search and rescue operations in the event of trouble. Divers and low lying vessels such as kayaks and underwater vehicles are nearly invisible in these conditions and the potential of being accidently run down become a quick reality.
Currently divers use a dive flag to mark their location where they are diving but have no RADAR reflecting device. Some kayakers mount a RADAR reflector to the deck of their kayak but it has little effect at the low elevation above the water. In addition, some underwater vehicles have employed an end-of-mission inflatable RADAR reflecting bag that is designed to float at the surface of the water. However, the reflecting bag is filled with CO2 and since it floats at the water surface, its elevation is often lower than a kayak's deck.